Cytokine gene polymorphisms and fatigue in breast cancer survivors: early findings.

Converging evidence from basic and clinical studies suggests a role for proinflammatory cytokines in cancer-related fatigue, although the etiology of elevated inflammatory processes is unclear. We examined single nucleotide polymorphisms (SNPs) in the promoters of cytokine genes as genetic risk factors for cytokine-related fatigue in 33 fatigued and 14 non-fatigued breast cancer survivors, focusing on promoter sequence polymorphisms in IL1B and IL6 associated with differential expression of proinflammatory cytokines. Predictors of fatigue included presence of at least one cytosine at IL1B -511 (95%CI=0.91-16.6, p=.007) and homozygosity for either variant of the IL6 -174 genotype (G/G or C/C; 95%CI=1.12-17.9, p=.027). Associations between fatigue status and IL1B genotype remained significant after covariate adjustment for demographic, biobehavioral and treatment-related factors. These findings provide preliminary evidence that polymorphisms in IL1B may serve as a potential risk factor for persistent fatigue in the aftermath of cancer.